The present invention refers in particular to joining thin parts together, such as sheets of metal etc., where the thermal expansion of the sheets along their large dimensions is large compared to the thickness of the sheets.
This description refers basically to joining such parts together by welding, brazing or soldering at their thinnest or smallest dimensions in any direction.
During the heating of such parts at their joining areas during a welding process, so as to fuse one or more of the parts, the heated surrounding areas expands due to their thermal properties. The amount of expansion can be different, due to the use of different materials for the parts. This causes the basic parts to deform and cause high mechanical force in the materials.
This is in particular the case if different materials are joined together. Due to the cool down conditions, the fused material(s) solidifies within the joint area, therefor freezing such thermally created stresses in the remaining solid parts, creating a final cooled part having a different shape than it was before welding. It should be noted, that extremely high mechanical tensions can be frozen into such welded products.
Very little is published about handling and reducting thermal expansion during the fusion welding process. Due to the freezing of the thermal expansion during solidification, the expansion problem occurs with similar and in particular dissimilar materials, such as during welding steel alloys to copper. Further, extremely thin parts are affected as well, in particular such parts have dissimilar dimensions.
An applied beam of energy for welding also has a positioning tolerance during the welding process and therefor heats the items with tolerance. This results in tolerances of thermal expansion as well. This disadvantage starts during the first moment of applying thermal energy and is also applied to the mechanical fixture holding these parts.